Allergy to azufaifa fruit and latex

. AZUFAIFA is the edible fruit of the azufaifo tree belonging to theRhamnaceae family. Only one case of urticaria and angiedema due to azufaifa has been previously published as an abstract (1). Thepatientwas a 38-year-oldnursewith a previous history of latex allergy (contact urticaria, rhinoconjunctivitis and asthma) and food allergy (banana, chestnut, kiwi and avocado). In September of 2000, she suffered from urticaria, angiedema, rhinoconjunctivitis, dyspnea, wheezing, abdominal pain, diarrhea and sickness, immediately after eating some azufaifas (that she previously tolerated). She progressively improved after treatment with subcutaneous epinephrine and intravenous corticosteroids and antihistamines, and her symptoms subsided 24 h later. Skin prick tests to common allergens (foods, pollens,mites,molds and epithelia) werenegative. Prick testwith a commercial latex extract (ALK-Abello) was positive. Prick-by-prick tests proved positive with latex gloves and crude extracts of azufaifa, avocado, chestnut, kiwi and banana.Total serum IgE was 33 UI/ml (Alastat, DPC). IgE antibodies specific to kiwi, banana, chestnut and avocado were, 0,35 kU/l; latex 2,07 kU/l and azufaifa 0,37 kU/l (CAP System, Pharmacia, Uppsala, Sweden). A SDS-PAGE was performed with an extract of azufaifa prepared by us following previous descriptions (2). Lyophilized crude extracts of avocado, banana, chestnut, latex and grass pollen and a commercial extract of olive (Inmunotek) and a recombinant chestnut class I chitinasewereused for the inhibition assays. The SDS-PAGE showed several bands from 15 to 60 kDa. IgE-immunoblotting with the patient’s serum revealed a single band of around 30 kDa. The recognition of this band was inhibited by a latex crude extract, but not by avocado, banana, chestnut, or pollens extracts. The recombinant chestnut class I chitinase extract weakly inhibited this band. Immunoblotting with the serum of the patient revealed a strong band of around 30 kDa in the chestnut chitinase recombinant. Immunoblotting with 19 control sera (5 non atopic and 14 atopic subjects) was performed. Only two of them (both sensitized to grass pollen) showed a strong detection of two bands of around 55 and 60 kDa. The serum which presented the strongest detection was used in crossreactivity assays .(Fig. 1). This serum showed inhibition by latex and avocado, but a greater inhibition was obtained with the grass pollen extract. It should be noted that this patient had not known sensitivity to azufaifa, avocado or latex. Several latex allergens have been cloned and sequenced. Hevein (Hev b 6.02) contributes to the increased prevalence of fruit allergies in individuals allergic to latex. It is a polypeptide of 43 amino acid residues, which shares high-sequence similarities with pathogenesis-related proteins (PR-3 and PR-4 3–5). Class I chitinases (PR-3 family) are monomers of 25–35 kDa, and contain an N-terminal region called hevein domain which shows cross-reactivity with latex hevein (4). Our patient recognized a single band of around30 kDa,amolecularweight similar to class I chitinases. It would be possible that the catalytic domain of chitinases could be involved in cross-reactions. Therefore, it could explain the crossreactivity between latex and azufaifa but not with chestnut, banana and avocado (cross-reactivity among this foods are mainly due to hevein domain). All these findings suggest that the sensitization in our case is different to that described for other fruits in the latex–fruit syndrome.As we have not sequenced the protein we cannot affirm that it is a chitinase and, actually, it would be possible that the sensitization could be due to another allergen.